Re: [Xen-devel] [PATCH RFC V6 1/5] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks

[Avi Kivity <avi@xxxxxxxxxx>]

On 04/23/2012 12:59 PM, Raghavendra K T wrote:
> From: Srivatsa Vaddagiri <vatsa@xxxxxxxxxxxxxxxxxx>
>
> KVM_HC_KICK_CPU allows the calling vcpu to kick another vcpu out of halt 
> state.
>     
> The presence of these hypercalls is indicated to guest via
> KVM_FEATURE_PV_UNHALT/KVM_CAP_PV_UNHALT.
>
>  #endif
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index e216ba0..dad475b 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -481,6 +481,10 @@ struct kvm_vcpu_arch {
>               u64 length;
>               u64 status;
>       } osvw;
> +     /* pv related host specific info */
> +     struct {
> +             int pv_unhalted;
> +     } pv;
>  };

'bool'.  Or maybe push into vcpu->requests.

>  
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 4044ce0..7fc9be6 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2147,6 +2147,7 @@ int kvm_dev_ioctl_check_extension(long ext)
>       case KVM_CAP_ASYNC_PF:
>       case KVM_CAP_GET_TSC_KHZ:
>       case KVM_CAP_PCI_2_3:
> +     case KVM_CAP_PV_UNHALT:
>               r = 1;
>               break;
>       case KVM_CAP_COALESCED_MMIO:

Redundant, since we can infer this from KVM_GET_SUPPORTED_CPUID.  But
please indicate this in the documentation.

>  
> +/*
> + * kvm_pv_kick_cpu_op:  Kick a vcpu.
> + *
> + * @apicid - apicid of vcpu to be kicked.
> + */
> +static void kvm_pv_kick_cpu_op(struct kvm *kvm, int apicid)
> +{
> +     struct kvm_vcpu *vcpu = NULL;
> +     int i;
> +
> +     kvm_for_each_vcpu(i, vcpu, kvm) {
> +             if (!kvm_apic_present(vcpu))
> +                     continue;
> +
> +             if (kvm_apic_match_dest(vcpu, 0, 0, apicid, 0))
> +                     break;
> +     }
> +     if (vcpu) {
> +             /*
> +              * Setting unhalt flag here can result in spurious runnable
> +              * state when unhalt reset does not happen in vcpu_block.
> +              * But that is harmless since that should soon result in halt.
> +              */
> +             vcpu->arch.pv.pv_unhalted = 1;
> +             /* We need everybody see unhalt before vcpu unblocks */
> +             smp_mb();

smp_wmb().

> +             kvm_vcpu_kick(vcpu);
> +     }
> +}
> +
>
>  /*
>   * hypercalls use architecture specific
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 42b7393..edf56d4 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1500,6 +1500,14 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
>               prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
>  
>               if (kvm_arch_vcpu_runnable(vcpu)) {
> +                     /*
> +                      * This is the only safe place to reset unhalt flag.
> +                      * otherwise it results in loosing the notification
> +                      * which eventually can result in vcpu hangs.
> +                      */
> +                     kvm_arch_vcpu_reset_pv_unhalted(vcpu);
> +                     /* preventing reordering should be enough here */
> +                     barrier();
>                       kvm_make_request(KVM_REQ_UNHALT, vcpu);
>                       break;
>               }
>

Hm, what about reusing KVM_REQ_UNHALT?

-- 
error compiling committee.c: too many arguments to function


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel